Perhaps the most significant finding was that investment in solar far surpassed wind last year. With solar investment up 36 percent last year and wind investment down 17 percent, spending on photovoltaic and solar thermal installations was almost twice as great as turbine outlays. Solar investment in 2011 came to $136.6 billion--more than half the global clean tech total of $260 billion--while wind investment was $74.9 billion.

"The largest single type of investment was the asset finance of utility-scale renewable energy projects," said the Bloomberg report. "This increased from a revised $138.3bn in 2010, to $145.6bn in 2011. Among the big projects financed in the last quarter of the year were the 288 MW Amrumbank West offshore wind farm off Germany for $1.3bn, the 272 MW Seigneurie de Beaupre wind farm phases one and two in Canada for $756m, and the 92.5 MW Hanas Ningxia Yanchi Gaoshawo solar thermal plant in China, for $354m."

The second largest category of clean tech investment was distributed energy, notably rooftop PV, which came to $73.8 billion. A surprisingly small category, on the other hand, was the highly touted smart grid, power storage, efficiency, and smart transport. Here investment spending came to just $19.2 billion, less than 7.5 percent of the world total. Another negative finding: Public and private R&D spending on clean tech dropped to $25.9 billion in 2011 from $31.5 billion the year before.

Another cautionary note, this one unmentioned by Bloomberg: The drop in wind investment suggests that costs are plateauing as the most attractive installation sites are saturated; though solar right now is soaring, strongly driven by ubiquitous subsidies and low Chinese production costs, we could soon see site saturation and plateauing costs here as well.